1. Field of the Invention
The present invention relates to copolyamides from aliphatic diamines, particularly hexamethylene diamine and either mixtures of adipic acid and terephthalic acid, or mixtures of adipic acid, terephthalic acid and isophthalic acid. In particular, it relates to copolyamides having a melting point(T.sub.m) below 320.degree. C., a glass transition temperature(T.sub.g) between 100.degree. C. and 120.degree. C., and mechanical properties similar to nylon 66.
2. Description of the Prior Art
100% hexamethylene terephthalamide(6T) polymer has a high T.sub.g and also a T.sub.m (about 370.degree. C.) too high for it to be melt processed. While replacing a portion of the terephthalic acid with isophthalic acid lowers the T.sub.m while preserving the high T.sub.g, the resulting 6T/6I (hexamethylene terephthalamide hexamethylene isophthalamide) copolymer has less crystallinity. Accordingly, copolyamides obtained from 66 (hexamethylene adipamide), 6T, and 6I in various ratios have been developed and applied in different industrial fields. For example, Japan Patent No. 46-18809 (71018809) discloses a copolyamide obtained from 10-50 wt% of hexamethylene adipamide(66), 10-50 wt% of hexamethylene terephthalamide (6T) and 10-55 wt% of hexamethylene isophthalamide (6I). The copolyamides are suitable for use as fibers.
Japan Laid open Patent No. 52-85516 (77085516) discloses a copolyamide fiber which is obtained from 20-70 wt% of hexamethylene adipamide(66), 15-45 wt% of hexamethylene terephthalamide (6T) and 15-35 wt% of hexamethylene isophthalamide (6I).
Japan Patent No. 46-28218 (71028218) discloses a complex polyamide fiber which is manufactured from a copolyamide prepared from 10-80 wt% of hexamethylene adipamide(66), 10-50 wt% of hexamethylene terephthalamide (6T) and 10-55 wt% of hexamethylene isophthalamide (6I).
U.S. Pat. No. 4,238,603 discloses a copolyamide fiber which is obtained from 2-15 wt% of hexamethylene adipamide, 45-68 wt% of hexamethylene terephthalamide, and 30-40 wt% of hexamethylene isophthalamide.
Japan Pat. No. 68-067801 discloses a fiber prepared from a copolyamide consisting of 10-80 wt% of hexamethylene adipamide, 10-65 wt % of hexamehtylene terephthalamide, and 10-55 wt% of hexamethylene isophthalamide.
U.S. Pat. No. 4,218,509 discloses a copolyamide fiber which is manufactured from at least 50 wt% of hexamethylene adipamide, 20-40 wt% of hexamethylene terephthalamide, and 2-20 wt % of hexamethylene isophthalamide.
U.S. Pat. No. 4,521,484 discloses the synthesis of copolyamide filaments which are manufactured by using at least 60 wt% of hexamethylene adipamide, 15-30 wt% of hexamethylene isophthalamide and 5-10 wt% of hexamethylene terephthalamide.
U.S. Pat. No. 4,603,166 and U.S. Pat. No. 4,603,166 disclose crystalline copolyamides having high heat deflection temperature, which are prepared from hexamethylene diamine, adipic acid, terephthalic acid and isophthalic acid at a mole ratio of about 100:5-35:65-95: 0-25.
U.S. Pat. No. 4,246,395 discloses a fiber-forming polyamide consisting of 5-20 wt% of hexamethylene adipamide, 40-75 wt% of hexamethylene terephthalamide and 20-40 wt% of hexamethylene isophthalamide. The fiber-forming polyamide has a melting point below 320.degree. C., a glass transition temperature above 115.degree. C. and good thermal stability.
U.S. Pate. No. 4,268,661 discloses copolyamides having a glass transition temperature of 140.degree. C.-170.degree. C. The copolyamides are suitable as engineering plastics and are manufactured from 0-15 mole% of hexamethylene adipamide, 0-50 mole % of hexamethylene terephthalamide and 50-100 mole% of hexamethylene isophthalamide.
Japan Patent Nos. 60-32980(94-32980) and 60-32979(94- 32979) disclose crystalline polyamides for injection molding. The polyamides comprise 30-95 wt% of hexamethylene adipamide, 0-40 wt% of hexamethyene terephthalamide, and 5-30 wt% of hexamethylene isophthalamide.
Japan Patent No. 31-26725 discloses aromatic copolyamides which are produced by polymerizing adipic acid, terephthalic acid, isophthalic acid and hexamethylene diamine in the presence of sodium hypophosphite.
Japan Patent No. 3007761 discloses polyamides prepared from (a) a dicarboxylic acid consisting of 0-70 mole% of adipic acid, 30-100 mole % of terephthalic acid, and 0-40 mole % of isophthalic acid and (b) hexamethylene diamine. The polyamides thus prepared are highly resistant to heat, water and chemicals and have high mechanical strength.
German Patent DE 3506656(1986) discloses copolyamides prepared from adipic acid, terephthalic acid, isophthalic acid and hexamethylene diamine with a weight ratio of adipic acid to mixture of terephthalic acid and isophthalic acid of 30-51:48.5-70. The weight ratio of terephthalic acid to isophthalic acid is 48.5-60:40-51.5. The copolyamides have higher T.sub.g and lower water absorption.
European Patent No. 121984 discloses a copolyamide comprising (A) hexamethylene adipamide, (B) hexamethylene terephthalamide and (c)hexamethylene isophthalamide wherein the mole ratio of the dicarboxylic acid moieties in (A), (B) and (C) is 5-35:5-35:60-90. An injection molding composition comprising the above copolyamides and 10-60 wt% of glass fibers or beads and/or mineral or graphite fibers has a heat deflection temperature of 240.degree. C.-305.degree. C.
Japan Laid Open Patent No. 6-287299 discloses a continuous process for preparing copolyamides. The copolyamides comprise the following recurring units: ##STR1## wherein the weight ratio of (I)/(II) is 55-80/20-45, (I)/(III) is 20-80/20-80 and (I)/(IV) is 55-90/10-45. The copolyamides are heat resistant and have lower water absorption.
Japan laid open Patent No. 06-287,300 discloses a copolyamide comprising the same recurring units (I), (II), (III) and (IV) and having the same weight ratio of (I)/(II), (I)/(III) and (I)/(IV). The copolyamide is crystalline and heat resistant.
European Patent No. 0 409 666 A2 discloses a polyamide composition comprising the following recurring units: ##STR2## wherein the mole ratio of the dicaroxylic acid moieties in the A, B, and C units is about 0.5-49.5/0-20/0.5-49.5 and wherein R is a divalent radical comprising ##STR3## and --(CH.sub.2).sub.6 -- in a mole ratio of about 0.5-50/49.5-0. The polyamide compositions have a glass transition temperature of 90.degree. C. or greater and an oxygen transmission rate of about 2.0 cc-mil/100 in.sup.2 -day-atm or less.
European Patent No. 0 291 096 discloses a novel crystalline copolyamide having high heat deflection temperature. The copolyamide comprises the following recurring moieties: ##STR4## wherein the mole ratio A:B:C is 60-90:35-5: 35-5.